1. Field of the Invention
The present invention relates to a roll control system in a vehicle such as an automobile, and more particularly, to an improvement of a roll control system which controls the rolling of the vehicle body based upon the rate of change of an estimated lateral acceleration with reference to the steering angle.
2. Description of the Prior Art
A roll control system in a vehicle such as an automobile is known as being adapted to control the roll stiffness of the vehicle in its quick turning as based not only upon the lateral acceleration as in normal turning but also upon the rate of change of an estimated lateral acceleration obtained from vehicle speed and steering angle velocity, in order to improve the responsiveness of the roll control, as described, for example, in Japanese Patent Laid-open Publication 61-81212.
On the other hand, it is well known in the art of car driving that, when the vehicle has drifted, i.e. when the rear part of the vehicle has made a side sliding toward the outside of the turn during a turning of the vehicle on a slippery road, the so-called counter steering, that is to steer the vehicle to the direction opposite to the turning, is sometimes effective in order to correct the running direction of the vehicle. However, when such counter steering is done while the vehicle is running under the roll control operating based upon the rate of change of a lateral acceleration estimated from vehicle speed and steering angle velocity, since the direction of turning of the vehicle and that of turning the steering wheel are opposite to one another, the rolling control will rather augment the rolling of the vehicle body.